Phyllodesmium is a genus of predatory sea slugs, aeolid nudibranchs, marine gastropod molluscs in the family Myrrhinidae.

These nudibranchs occur in the tropical Indo-Pacific Ocean and warm temperate waters of Japan, Tasmania and South Africa.

The nudibranchs in this genus often show extraordinary mimicry, each species very closely resembling its prey species, which are octocorals, a kind of soft coral.

Some of the species are also unusual in that they are able to utilize zooxanthellae from their prey, in a symbiotic relationship that provides them with extra nutrition from photosynthesis, hence they are commonly called "solar-powered" sea slugs (also see the Sacoglossa).

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